The invention relates to systems and methods for unloading trays loaded with articles, along a supply conveyor on which the trays to be unloaded are delivered.
Systems and methods of this type are used for automatic unloading of trays loaded with articles, wherein the unloading process is carried out during ongoing conveyor movement, incorporated into supply and discharge conveyor technology.
Trays are often used in automatic storage and picking systems. These trays allow articles, which are often highly dissimilar in their dimensions and/or material properties or which need to be transported and stored very gently, to be handled in logistics systems quickly and in a controlled and uniform manner in spite of this dissimilarity in the articles.
Commercially available trays have very different characteristics. For example, trays are known which have a closed base, or with bases which have slits or holes (for lifting the articles out) or even with inserted bases which can be lifted out in combination with slits and/or holes in the base.
In many cases, trays are loaded and unloaded manually. Applications are also known in which trays are both loaded and unloaded automatically.
While automatic loading is mostly carried out on the move, automatic unloading is typically carried out at specific stations, wherein the tray is stopped at these stations during unloading. This stoppage wastes valuable time, and special equipment (e.g., a device for lifting the articles out and pushing them away) is also generally required at these stations.
For instance, from DE 103 13 576 A1 it is known to use trays with a peripheral edge and with holes in the base so that the articles can be lifted out from below by lifting pins. The articles are then pushed by means of a rake (cf. para. [0013] and [0053]).
From DE 40 23 290 C1 it is known to lift roof tiles from their frame-like support for the purposes of engobing or glazing and then to set them down again, for which purposes a lifting member engaging from below through the support frame is provided, which lifts the roof tiles from the support frame and sets them down during constant conveyance, i.e. during movement.
However, this method can be used only when the movements of the roof tile conveyor and the rake conveyor are synchronised, since the lifting member must engage the support frame with its pins precisely through the openings in a perpendicular manner from below in order to lift the whole roof tile at the same time so that the lifting members are guided in a parallel manner. The lifting member must also be precisely adapted to the shape of the roof tiles in order to support them, meaning that the disclosed system is not very flexible. In addition, the speed is low since the lifting member must raise the roof tiles for a certain time so that they can be engobed or glazed.
The device shown therein is thus not suitable for modern logistics applications in which dissimilar articles need to be processed “simultaneously” at high speed and in a selective manner.
From the applicant's own DE 92 11 139 U1, in each case a system is known for unloading trays loaded with articles having a first supply conveyor on which the trays to be unloaded are delivered, which are provided with a peripheral raised edge and a base provided with apertures, and having lifting members of a lift-out device, which engage from below through the apertures and are designed to be moveable in the conveyor direction, a corresponding method also being known therefrom. On the base of the trays a flat transport plate possibly lying thereon is provided for the articles, which is raised by the lifting members so that the articles lying on the transport plate can be stripped off.